Polymers degrade over time. Molecular composition, processing, storage, and use conditions are all factors that can affect the degradation rate. For example, the hydrolytic degradation rate of a polyether block amide copolymer has been found to increase when tungsten carbide is added to make radiopaque tips for catheters. Such catheter material degradation can limit shelf life and increase costs. Methods and additives that extend the shelf life of hydrolytically unstable polymers are therefore needed.